Structure and decay width of the Θ+(1540) in a one-gluon exchange model

The mass and decay width of the Θ+(1540) with isospin 0 are calculated in a constituent quark model comprising quarks. A correlated basis is used in a non-relativistic five-particle model, and the Θ+ is identified with a resonance state described as a solution stable against changes in the basis. With the use of a one-gluon exchange quark–quark interaction, the mass is found to be larger than 2 GeV, in a sequence of spin-parity , , , and only the state has a small width to the nK∗+ decay. By shifting the calculated mass to around 100 MeV above the N+K threshold, the level to be identified with the Θ+(1540) has spin-parity or , though in the latter case it cannot decay to the nK+ channel. In addition it is conjectured that other pentaquark states with different spin-parities exist below the Θ+(1540). The structure of the pentaquark states is discussed in terms of the densities and two-particle correlation functions of the quarks and in terms of the wave function decompositions into a baryon–meson model and into a diquark-pair model.